In an optical communication network, optical signals having a plurality of optical channels at individual wavelengths (channels), are transmitted from one location to another, typically through a length of optical fiber. An optical cross-connect module allows switching of optical signals from one optical fiber to another. A wavelength-selective optical cross-connect, or wavelength selective switch (WSS), allows reconfigurable wavelength-dependent switching, that is, it allows certain wavelength channels to be switched from a first optical fiber to a second optical fiber while letting the other wavelength channels propagate in the first optical fiber, or it allows certain wavelength channels to be switched to a third optical fiber. An optical network architecture based on wavelength-selective optical switching, has many attractive features due to the ability to automatically create or re-route optical paths of individual wavelength channels. It accelerates service deployment, accelerates rerouting around points of failure of an optical network, and reduces capital and operating expenses for a service provider, as well as creating a future-proof topology of the network.
In some cases the functionality of multiple wavelength switches may share a common set of optical elements such as lenses, dispersion elements and a spatial light modulator. Such wavelength selective switches may exhibit undesirable levels of cross talk between the various channels of the functionally different switches.